Current Control of VSI-PWM Inverters

The inherent limitations of commanding voltages and currents in a three-phase load with an inverter are examined. An overview of several current controllers described in the literature is presented, and computer simulations are used to compare performance. A switching diagram is developed which reveals some of the operating characteristics of hysteresis controllers. For ramp comparison controllers, a frequency transfer function analysis is used to predict the line currents and provide some insight into the compensation required to reduce the current errors.